This project is in response to the Recovery Act Limited Competition: Research to Address the Heterogeneity in Autism Spectrum Disorders (RFA-MH-09-172). The proposed project will determine the applicability, reliability, and validity of the newly revised computer-adaptive version of the PEDI (PEDI-CAT) for children and youth with ASD. In the first phase of work we will involve parents of children and youth with ASD as well as professionals working with this population to evaluate the adaptive behavior item pool of the current PEDI-CAT. We will focus on two major questions: 1) Whether there are items that would be difficult for parents to answer, given the unique features of ASD and 2) Whether additional items are needed to fully represent the areas of daily life more affected by ASD. Data from the reviews will be used to modify or write new items to be tested as part of a new item pool. In the second phase of work we will conduct a web-based study to obtain PEDI-CAT data (including responses to new items) from 600 parents of children and youth with ASD between the ages of 3 and 21 years. We will then calibrate the items using item-response theory (IRT) methods and evaluate the performance of the new adaptive behavior items. The data from this sample will be used to build a modified PEDI-CAT for children and youth with ASD and to examine the relation between estimated scores generated from the ASD CAT and those obtained from administering the entire item pool. We will also examine items from the ASD sample perform as would be predicted from the IRT model derived from the normative sample. The primary objective of this project is to achieve a major advance in the measurement of adaptive behavior in children and youth with autism spectrum disorders (ASD). Availability of a brief and precise assessment of daily function, the PEDI-CAT (ASD) will greatly improve the quality of information obtained on the adaptive behavior of children and youth with ASD. This new instrument will enable more sensitive tracking of change in this critical outcome across childhood and adolescence as well as examination of the relation between variations in core symptoms and functional outcomes in this population. PUBLIC HEALTH RELEVANCE: The PEDI-CAT (ASD) will facilitate significant advances in ASD research and clinical services by providing a brief but precise, psychometrically sound assessment of daily function in home and community. The instrument will greatly improve the quality of information obtained on the adaptive behavior of children and youth with ASD and make possible more sensitive tracking of changes in this critical outcome across childhood and adolescence.